Unlike the traditional network architecture, which integrates both the data plane and the control plane in the same box (e.g., a network element such as a router), a split-architecture network decouples these two planes and executes the control plane on servers (controllers) that might be in different physical locations from the forwarding elements (switches). The use of a split architecture in a network enables the simplification of the switches and shifts the intelligence of the network into a number of controllers that oversee the switches.
The tight coupling of the forwarding and control planes in a traditional architecture usually results in an overly complicated control plane and complex network management. This is known to create a large burden and high barrier to new protocols and technology developments. Despite the rapid improvement of line speeds, port densities, and performance, the network control plane mechanisms have advanced at a much slower pace than the forwarding plane mechanisms.
In a split-architecture network, controllers collect information from switches, and compute and distribute the appropriate forwarding decisions to switches. Controllers and switches use a protocol to communicate and exchange information. An example of such protocol is OpenFlow (see the OpenFlow 1.1 Specification), which provides an open and standard method for a switch to communicate with a controller, and it has drawn significant interest from both academics and industry.